Some patients cannot control tooth attachment loss (periodontitis) after intensive oral hygiene therapy. Recently, successful therapy was found to depend on an increased prevalence of "beneficial" relative to "pathogenic" bacteria in gingival sulci. A simple procedure based on this finding is proposed: an enzyme immunoassay to measure the concentration of specific for Actinomyces spp. (A-Ab), a major component of the beneficial flora. The specific aim of this Phase 1 proposal is to compare the A-Ab concentration in patients who are either refractory or responsive to therapy. High and low A-Ab concentrations will be separated by a cutoff value derived from antigen/antibody precipitation and enzyme immunoassay. Near this value, the determination of high/low A-Ab response requires measuring a control antibody, to unstable D- alanyl esters of lipoteichoic acid from streptococci (S-Ab). The Phase 2 aims are to determine: (1) whether therapy alters A-Ab concentration in longitudinal studies; (2) whether A-Ab concentration affects treatment needs; and (3) whether S-Ab content can be measured with stable surrogate antigens. The proposed assay should identify refractory patients faster and more accurately than clinical skills, or assays for pathogenic bacteria or host-produced destructive enzymes at gingival sulci. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE